(Or behaviourism, not to be confused with behavioralism in political science) An approach to psychology based on the proposition that behavior can be researched scientifically without recourse to inner mental states. It is a form of materialism, denying any independent significance for the mind.

One of the assumptions of many behaviorists is that free will is illusory, and that all behaviour is determined by a combination of forces both genetic factors and the environment, either through association or reinforcement.